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Home /  Appliance Maintenance / 6 Reasons Your Air Conditioner Is Blowing Hot Air
last_updated_date Last updated: January 16, 2024

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6 Reasons Your Air Conditioner Is Blowing Hot Air

Can you imagine how you would feel if your Air Conditioner is blowing hot air instead of cold? Air Conditioners are rather complex, with a variety of parts and internal systems. HVAC units blowing hot air are quite common and if this problem persists, then you need to get it checked.

6 Reasons Your Air Conditioner Is Blowing Hot Air

To analyze the reasons your air conditioner(AC) is blowing hot air, we need to understand the basics of how an air-conditioning system works.

About Air Conditioning Systems

To understand why a new, seemingly functional AC is suddenly not performing, we need to understand the mechanics of an Air Conditioner in simple terms. Heating Ventilation and Air Conditioning as it is technically referred to, is the technology of Ventilating a room or car based on the principles of thermodynamics, fluid mechanics, and heat transfer facilitated by electricity. Let us break it down – after all, the first step to fixing is thoroughly understanding the problem.

Air conditioning a space primarily involves providing high indoor air quality, temperature control, oxygen replenishment and removal of moisture. Additionally, it also includes the removal of odors, smoke, heat, dust, airborne bacteria, carbon dioxide, and other gases as much as possible. The system introduces a small quantity of fresh outside air and helps circulates this air in the room, thereby preventing stagnation of stale air.

Air Conditioners for a small building come in different types. The most common are Window Air Conditioners and Split Air Conditioners. Larger spaces may need Package units. The largest is the Central Air Conditioning systems which are used in industrial buildings, restaurants, hospitals, and offices.

Let’s start by addressing a window or a split which has a problem with dispersing cold air into the room. The essential parts of an air conditioner are the compressor, condenser and expansion valve, fans or blowers, thermostat, evaporator, chemical refrigerant and cooling fluid.

How Does an Air Conditioner Work?

An HVAC deals with both hot and cold air conditioning systems. Here we are addressing only cold conditioning where air conditioners do not produce cold air. They cannot produce cold air in the way a stove produces heat, because cold is the absence of heat and cannot be produced. Put simply, Air Conditioners use the refrigeration principle to chill indoor air, taking advantage of a simple law of physics – when a liquid converts to a gas, it absorbs heat. Air conditioners exploit this feature of conversion by forcing special chemical compounds called Refrigerants to evaporate and condense over and over again in a closed system of coils. Refrigerants like Freon have properties enabling them to change liquid or gaseous states, at relatively low temperatures. If this feature malfunctions, and if your air conditioner is blowing hot air, then a mechanic needs to be called.

Air conditioners also have Fans or Blowers that disperse warm air from inside the room over these cold refrigerant-filled coils. The refrigerant circulates continuously to remove more and more heat from the room until the indoor air temperature reaches what is set on the Thermostat.

The Evaporator or the evaporator core is the part of the Air Conditioner where hot air from the room circulates around the refrigerant coil exchanging its heat with cold air from the later. The cold air is blown back into the room.

This is where the Compressor, Condenser and Expansion valve play a part in the conditioning. The main difference between the compressor and condenser is indicated by their names. It first compresses the gaseous hot refrigerant coming from the evaporator. The condenser is responsible for taking the pressurized gas from the compressor and changing it into a liquid vapor. This pressurized process is one that is often the cause of your problem. If your air conditioner is blowing hot air, then chances are that this highly pressurized mechanism has malfunctioned because of dust and dirt blockages.

The transformed refrigerant then passes through an Expansion valve. Think of a can of Aerosol, does it feel cold when it leaves the pressurized can even if the ambient temperature is hot? Same principle here. The pressurized refrigerant cools rapidly and is back to exchange heat for its cold from the hot room air. Fascinating mechanics, with two independent circulation paths working continuously and mutually transferring temperature.

The cold air is blown out, back into the room through a Filter. With proper maintenance, this system performs perfectly. An air conditioner will stop working if the compressor gets faulty. Otherwise, faults are mostly repairable. In this context, a seemingly good air conditioner spewing hot air is symptomatic of one or many of the following issues.

Fortunately, most of these issues can be solved without the help of a HVAC professional. Let us have a look at the different possibilities that can cause the conditioner to blow hot air.

Why Your Air Conditioner is Blowing Hot Air

Why Your Air Conditioner Is Blowing Hot Air

1. Faulty Settings

Thermostat set to a higher temperature and other setting faults are common. It happens! Especially with today’s light touch remotes. Before jumping to conclusions if your air conditioner is blowing hot air, make sure you check if the basic settings are to your requirement, including the timers and fan speed.

The fan setting can blow hot air, as it serves the purpose of air circulation during cooler days. On a particularly hot day, if the fan is set to on, it will blow air through the vents whether the system is actively cooling the space or not. Set the remote to auto if you want only cool air.

The dry setting during dry weather is also a setting that can make the space uncomfortable. It works best only in humid weather. At other times, this setting interferes with the thermostat, and can give the feeling of hot air being blown through the vents.

Many states in the country experience weather extremes on both ends of the spectrum. Most often our HVACs serve the purpose of both heating and cooling, depending on the season. A heat setting instead of cool may sound rather improbably, but there is no harm in checking.

2. Clogged Air-filter

A dirty air filter clogged with dirt can decrease the efficiency of your Air Conditioner by 20% or more. Filters need to be cleaned regularly and periodically changed too. It is good to remember that dust, dirt and lint are all around us. People and pets shed hundreds of skin cells and hair follicles every day. These are so tiny that they tend to float in the air, and end up getting sucked into the air filter. Apart from that the filter absorbs grime and smoke as a part of its suction from the room.

Once the filter is fully saturated, you cannot expect chill air to blow through. This is yet another reason why your air conditioner is blowing hot air.

Simply put, hot air from an air conditioner can sometimes mean that it’s time to clean or change your filter. A reasonably new and clean filter can be washed and dried before putting it back on. While cleaning the filter, consider checking the evaporator coil behind it. Sometimes the evaporator coils get caked in dirt and grime preventing heat transfer, thereby dispersing hot air. So that is yet another reason for hot air easily rectified by cleaning. Switch the system off and clean the coils with a soft dry cloth.

3. Clogged Condenser

The condenser is exposed to the exterior of the building. Considering that it is covered only partially in order to help dissipate heat, it is not secure from dirt. Because the condenser is outside, weeds can grow around it and debris like leaves, twigs, cobwebs and other dirt can gather at the base of the casing, causing an airflow obstruction.

Cleaning the condenser casing as well is very simple. Make sure you switch off the system before setting to clean it with soft cloth.  A mild soap and water will not harm the condenser casing because it is designed for external weather. Clean once more with a dry cloth before switching it on.

4. System Low on Refrigerant

The refrigerant does not need to be replaced often. So if everything is alright with respect to the issues mentioned above, but you are still facing hot air you could be facing a refrigerant leak.

A refrigerant leak is caused by cracks or holes in the coils which sometimes wear out due to continuous usage of the system.

In case of a refrigerant leak, the Air Conditioner unit will take air from the outside and pass it into your room, without cooling the air. Minor refrigerant leaks appear as tiny bubbles on the evaporator coils, that is the beginning of a refrigerant leak. Larger leaks become noticeable by a ether like odour emanating from the machine along with the hot air. A refrigerant leak should be immediately reported to your HVAC professional.

5. Outdoor Unit is Non-Functional

The condenser fan may have stopped working due to a circuit trip or non-maintenance of the outdoor part of the Air Conditioner unit.

This is easily recognizable, as you will notice that you have stopped hearing the familiar hum of the external unit. Call for a visit by your HVAC professional, DIY for such damage or malfunctions can do more harm than good.

6. A Frozen Evaporator Coil

The evaporator coil can freeze sometimes, which can block the cool air flowing into your home. Inside the unit, condensation can occur on the evaporator coils. This condensation can keep building up and lead to freezing if the thermostat is set really low on a very hot day. To prevent this from happening, you should keep your thermostat on Auto. It also makes sense to have the AC overhauled at the beginning of summer.

To fix the frozen evaporator coil, turn the conditioner off and let it thaw. After about an hour or two, it should be safe to turn it back on. If this happens once in a while due to temperature extremes or you forgetting to turn on auto, then it can be fixed as mentioned above. However, successive freezing could mean a deeper problem. So call a technician before further damage occurs.   

To sum up, it is absolutely essential to keep your conditioner clean and free of dust both on the inside and the outside. Everything from cleaning the filter pad to calling the maintenance man and having him give your Air Conditioner unit an overhaul regularly has to be done. It is important to know the common mistakes that HVAC users make, so you can avoid them. The explanation about how Air Conditioner work has to be sufficient to bring to your attention its complexity. Like humans, machines need rest too!

Considering a Home Warranty

Repairing your HVAC can turn out to be an expensive affair if your system is faulty and requires repair visits from the serviceman. ACs have become a part and parcel of our daily life and we find it really difficult to manage when they break down. It is also difficult to find a knowledgeable repairman whom you can trust to sort out the issue. A simple solution to this problem would be to buy a home warranty. However, there are somethings that you need to know about home warranties before you invest in one from your home. It is also important to research and read through reviews on home warranty companies that may interest you. It is a step that cannot be skipped.

Let us know if you have any questions related to home warranties in the comments section below. We are more than happy to help you out with your home warranty buying process.

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